/Engine/Source/Runtime/Engine/Public/Streaming/TextureMipDataProvider.h
Return the next value StartingMipIndex (for the next provider). Must be FTextureUpdateContext::CurrentFirstMipIndex to indicate that all mips have been handled.
int32 GetMips ( const [FTextureUpdateContext](API\Runtime\Engine\Streaming\FTextureUpdateContext) & Context, int32 StartingMipIndex, const FTextureMipInfoArray & MipInfos, const [FTextureUpdateSyncOptions](API\Runtime\Engine\Streaming\FTextureUpdateSyncOptions) & SyncOptions )